Brake



29, 1936. R. s. SANFORD |-:r AL

BRAKE Filed Feb. 20, 1933 3 Sheets-Sheet 2 llllllll INVENTORS. Ray 6.zuw-oea ATTORNEY.

Dec. 29, 1936. R. SQSANFORD El AL 2,065,077

BRAKE Filed Feb. 20, 1935 3 Sheets-Shet s INVENTORS. v For 6 SANFORDfin/ L. 0. MDSWORTH ATTORNEY Patented Dec. 29, 1936 UNITED STATES PATENTOFFICE BRAKE Roy S. Sanford, South Bend, Ind., and Frank L. 0.Wadsworth, East Liberty, Pa., assignors to Bendix Aviation Corporation,South Bend, Ind., a corporation of Delaware Application February 20,1933, Serial No. 657,692

23 Claims.

binding or dragging between the surface of the drum and the brake shoes.The present invention aims to overcome this objection by an automaticadjusting device which is normally operable only on reverse braking.

In the several embodiments herein illustrated a backing or face platehas associated therewith a rotatable drum and a friction .device mountedon the backing plate for cooperation with a brake drum. The frictiondevice comprises a floating ringjor band which is made up of twoadjustably connected members and which is arranged to anchor at one endwhen the drum is turning in one direction and at the other end when thedrum is turning in the'reverse direction.

The ends of the band or friction element are moved apart by a floatingcam or other actuating means operated by a cable or linkage, and themovements of the friction element or of the operating means, in reversebraking, is utilized to operate an adjusting means for the frictionelements.

One object of the invention is to provide a simple and efficient meansfor automatically adjusting the brake shoes or brake band as the brakelining wears, .so as to maintain a substantially constant clearancebetween the brake drum and the shoes,.when the brake is off and thuseliminate the necessity for any manual adjustment of the parts duringthe life of the lining.

Another object of the invention is to provide an automatic adjustingdevice for the friction elements of a brake normally operable only onreverse braking, but which may also become temporarily operable onforward braking if the wear or clearance is, for any reasonabnormallyincreased in the intervals between two successive reverse brakingoperations.

A further object of the invention is to provide means for adjusting thefriction elements of a brake which may be operated either by themovement of the shoes or brake band, or by motion of the cable, oractuating means for effecting this movement.

Other objects of the invention will appear from the followingdescription taken in connection with the drawings, which form part ofthis specification, and in which:

Figure 1 is a vertical sectional view of a brake of the two shoe type,looking toward the inner face of the backing plate and illustrating thefriction elements and the adjusting means therefor in side elevation;

Figure 2 is an enlarged detail view substantially on line 2-2, Figure 1;

Figure 3 is a vertical sectional view of another form of brake mechanismembodying the invention;

Figure 4 is a similar view of a third embodiment of the invention;

Figure 5 is a cross section on the line 5-5, Figure 4;

Figure 6 illustrates an application of the invention to a front wheelbrake;

Figure 7 is a side elevation of a part-of the construction as seen onthe line 'l'l, Figure 6;

Figure 8 is a vertical sectional elevation of a fifth embodiment of theinvention;

Figure 9 is a sectional view on line 99, Figure 8; and

Figure 10 is a partial section on the line I 0-l0 of Figure 6.

Referring to the embodiment of the invention shown in Figures 1 and 2,l0 represents a fixed support such as a backing plate. The backlng platehas associated therewith a rotatable drum I! which may be secured to awheel, not shown, and positioned on the backing plate is an anchor' l4and 'suitable steady rests Iii-and l8.

Positioned for movement on the backing plate I0 is a friction elementincluding a primary shoe 20 and a secondary shoe 22 supported by -thesteady rests. The shoes are of the conventional type each comprising aweb 24 supporting a rim 16 to which is secured a suitable lining 28adaptahle for cooperation with the braking surface of the drum.

The articulated ends of the shoes 2i and 22 are connected by a suitableadjusting device 30 comprising a member including rightand lefthandthreads 32 and}! and a ratchet wheel 36, The opposite ends of the shoeshave shoulders 38 and 40 notched to engage the anchor l4; and looselypivoted on the anchor, between the shoulders 38 and-'40 is a floatingcamlever 12 connected to and operable through a tension member or draftcable 4|, extending through a conduit abutment l6,

on the backing plate III to a suitable power operating means. Acompression spring 48 is interposed between the abutment 46 and thecable connection to the cam lever 42 for the purposeof Ii assisting thereturn movement of thecable when the operating tension therein isrelieved. The shoes 20 and 22 are connected by springs 50 and 52 whichalso serve to return the friction elements to the off position and tomaintain them in proper spaced relation, onclearanc'e with respect tothe brake drum when the brake is released.

Pivoted on the backing plate II is a lever 54.

pivotally connected at one end to a bar 56 slidable radially on thebacking plate. The bar 56 is provided with a longitudinal slot or groove56 receiving the ratchet wheel on the adjusting member, and pivo'tallysecured inthe slot is a pawl 60 urged into engagement with the ratchetwheel 36 by a spring 62. The intermediate portion of the lever 54 isplvotally connected by a link 54 to one endof a lever 66 pivotallymounted on the backing plate at 68 and provided at its opposite end witha projecting lug 10. The levers 54 and 66 are 0011-! 25 nected by astrong tension spring" normally imposing suflicient pull on the lever 54to hold it against a stop 14, in which position there is no relativemovement between thepawl 60' on the bar 56 and the ratchet wheel 36 onthe adjusting member.

The cam lever 42 carries an adjustable stud 16 adapted-to engage the lugIII on the lever 66 when I the .brakes are applied in reverse braking,and

to impose suflicient pressure thereon to actuate j the lever 54.Movement of the lever 54 slides the bar 56 radially outward, andduringthis movement the pawl 56 rides over the teeth of the ratchet wheel 36,without imparting any motion thereto. When the brake is released thespring I2 returns the'parts to their normal positions, and as the bar 55moves radiallyinward the ondary shoe 22 through the adjusting member 30,and results in holding the heel end of this shoeagainst the anchor I4.In this operation,. the cam lever 42 moves about its point of contactwith the shoe 22 at point I8 andthe end of the adjustable stud I5travels in the circularpath indicated by the dotted lines 86. This pathof movement is to the right or inside of the lug III on the lever, andunder normal conditions of clearance there is, therefore, no actuationof the adjusting device in forward braking.

When the drum is rotating counterclockwise the shoe 22 moves away fromthe anchor and the shoe 26 is held against the anchor. In thisoperation, which is reverse braking, the cam .lever 66 pivots on thecenter 62, and the endof the stud I6 moves in the curved path 64, andwhen the initial clearance has been increased by a small amount of wearthis movement is suillcient to bring the stud into engagement with thelug ll,

and thereby rock the levers 66 and 54 by-an amount which is proportionalto the wear. This rocking movement slidesthe bar 56 radially outward bya corresponding amount. When .the brake is released friction on thescrews 32'and' 34 76 is reduced, due to the removal of the load, and

the spring 12-.then returns the-parts totheir normal positions therebycausing the pawl 66 to engage and rotate the ratchet wheel and the rightand left threaded members 52 and 34,.to effectively readjust thelengthof the friction element .by the requisite amount andreestablishthe initial clearance between the brake drum'and th Y lining on thefriction element. I

By adjusting the stud I6 the amount of spread- V ing or take up movementeflected by each re-v verse braking operation may-be accuratelypredetermined and controlled, so as to hold the. variation in clearancedue to wear or other causes within any desired limits.

It will be noted that the effective length'or leverage of thetcam lever42 is less in forward braking (when the lever is rot atimpabout-the,

fulcrum point 16) than it is in reverse braking (when it rocks on thefulcrum 62); andthat as a consequence of this the arcuate movement ofreverse braking. This diflerence in arcuatemove-v ment would normallyprevent the stud I6 from engagingwith the lug l0 even if the paths-J6and 64 were coincident. But if an excessiveorunusual clearance should atany time be established between the normal automatic readjustmentsateach reverse braking operation, the resultant abnormal movement of thecam-lever in forward braking would bring the stud I6 into engagementwith the body of the lever 66, (inside of the terminal lug 10), and thusserve to take up a portion of this excess clearance before the nextcompletereadjustment is eflected by the succeedingreverse brakingoperation. The amount of such temporary or femergency readjustment mayin all cases be controlled and limited by varying the length or offsetof the lug I0 from the body of the lever. This will prevent the takingup of such a large amount of temporary clearance or lost motion as mightresult from excessive thermal expansion, and thus resuit in a binding ordragging of the parts when the brake drinn cools down;

Another embodiment of the invention is illustrated in Figure 3. In thisembodiment a backing plate Illll associated with a rotatable drum in haspositioned thereon a pair of brake shoes I 64 and I06. The shoes havetheir articulated ends connected by an adjusting device shown generallyat I08, and the other ends of the shoes have. notched shoulders IIlla'ndII2 engaging spaced anchors'II4 and H6.

A floating operating cam lever H6 is positioned on a pivot pin I26 onthe backing plate between the anchors H4 and II 5, in thrust engagementwith the shoulders H6 and H2. The force applying endof the lever m isbifurcated. An

axleis supported by the bifurcations and joure.

nailed on the axle between the bifurcations is a pulley I22. A yoke I24is supported by the axle and the yoke is -connected by a suitable springI26 to the shoe I'l4. This pulley has its perlph-' ating means, notshown. A compression spring, I42 is wound onthe cable between theconduit.

abutment I40 and a dog I44 adjustably positioned on the cable. As shown,the dog is adapted to slide on a suitable guide I48 on the backingplate.

The shoes I04 and I06 are connected by a return spring I48. The shoe I04is connected by an auxiliary return spring I50 to a fixed support I52 onthe backing plate, and the shoe I06 is connected by an auxiliary returnspring I54 to the fixed support I52. These springs assist in returningthe shoes to the oil position and in retaining the shoes when in thisposition in proper spaced relation to the drum.

' The adjusting device I08 includes a wedge I56 movable between thearticulated ends of the shoes by a screw I58 having a flange I60engaging the shoes and a ratchet wheel I62. A bar I64 slidable on thebacking plate between suitable guides I66 is slotted to receive theratchet wheel and positioned on the bar in the slot is a spring pressedpawl I68 engaging the ratchet wheel. The bar I64 is attached to theguide I66 by a tension spring I10 and pivotally connected to the bar I64is a lever I12. This lever is connected by a link I14 to the shoe I06,and the free end of the lever I12 is provided with a projection lug I16and an ment of the cable (which in this instance is substantiallygreater in forward braking than in reverse braking) does not affect theposition of n t d by a forward braking operation through" the slidablebar I64.

When the drum is revolving in the opposite direction the shoe I04 movesaway from the anchor H4, and the shoe I06 is held in engagement with theanchor II6, thereby maintaining the fulcrum link I14 and the lever I12in full line position and retaining the lug I16 in the path of action ofthe dog I44.

Under these circumstances any excess movement of the operating or draftcable, which may result from additional clearance due to wear of.

the lining, will bring the lug and dog elements inoperative engagementand will rock the lever I12 on its pivotal connection with the fulcrumlink I14, thereby sliding the bar I64 to the right. In this movement thepawl will ride on the teeth of the ratchet wheel.

When the brake is released the spring I10 will return the parts to thefull line position against a suitable stop I15, and in this returnmovement the pawl I68 will engage the ratchet wheel and turn theadjusting screw I58 by a predetermined amount, which is just suflicientto take up the wear of the friction lining and restore the usualclearance between the drum and the friction element. The amount of wearwhich may be permitted between two successive automatic adjustments maybe controlled and regulated by the setting of the dog on the operatingor draft cable.

If for any reason the amount of clearance is abnormally increasedbetween the two successive reverse braking adjustments a temporary oremergency adjustment suflicient to maintain a pedal'reserve for anexcessive expansion, may be the medium of the collar I18 which may be soset that it will be engaged'by the/dog on the cable when the cablemovement exceeds that required for normally setting the brakes in suchan opwhen the heated and expanded drum eration. The amount ofsuch anemergency ad'- justment can be controlled by the setting of the collarso that the take up effected at such times is 'never suflicient to causethe brakes to drag returns to normal size.

Another embodiment of the invention is illustrated in Figures 4 and 5.In this embodiment a backing plate 200 has associated therewith arotatable drum 202. Spaced anchors 204 and 206 are arranged on thebacking plate and movably positioned on the backing plate is a frictionelement comprising a split band 208 having reinforced separable ends 2I0and 2I2 provided with openings 2I4 and 2I6 for the reception of theanchors 204 and 206 respectively. The band has suitably secured theretoa'friction lining 2I8 adaptable for cooperating with the braking surfaceof the drum, and the band is retained when the brake is in the offposition, in proper spaced relation to the drum by a plurality ofsprings 220 connected between the band and fixed supports on the backingplate.

The separable ends of the band are shouldered as indicated at 222 and224. These shoulders support an operating cam lever 226. As shown, thelever has arranged thereon spaced rollers 228 and 230 positioned on theshoulders 222 and 224' respectively. The force applying end of the leveris connectedby a link 232 to one end of a bell crank lever 234 pivotedon the backing plate at its knee 236. The other end of the bell cranklever oper- -the roller 228 on the actuating cam.

One end'of the screw 244 carries a lever'252 provided with a reversepawl 254 adapted to engage the teeth of a' ratchet wheel 256 and rotatethe wheel in a counterclockwise direction to move the wedge-shapedmembers 240 and 242 to .eflect circumferential movement of the block 246and adjust the over-all length of the band.

The free end of the lever 252 is connected to a reciprocable bar 258which carries, at its outer extremity, an adjustable lug 260 and it isprovided at an intermediate point in its length, with a pin 262 whichengages a bracket 264 on the backing plate. -The link 232 carries anadjustable collar 266 adapted to engage, at times, with the head of thelug 260, and a second adjustable member 268 provided with a slotted armembracing the sides of the bar 258, and adapted to engage at othertimes, with the stein of the member 260.

Mode of operation-When the brake is applied to, stop forward movement ofthe car, the drum is rotating in the direction of the arrow A, the

block 246 and the primary end of the ring or band is moved away from theanchor 206 and in this movement the engagement of the pin 262 with thebracket 264 rocks the bar 258- to the left or away from the link 232 andcarries the lug 260 out of line of action of the collar 266 on the link232, so that the normal range of operative movement of the particularelements 226 and 232 will not actuate the adjusting mechanism.

the'anchor 288 and-the parts 288 and 288 will remain in the full lineposition, and under these circumstances any excess movement ofthe-actu-. ating link 282 -which in this case is greater inreverse-will, cause the collar 288 to engage the head. of the lug 288and rock the pawl lever 282 in a clockwise direction by an amountdependent upon and proportional to the excess movement.

When the brake is released a compression spring 218 interposed betweenthe bracket 288 and the lever 282 will return the parts 282 and i288 totheir neutral positions; and in this return movement the pawl-willengage the ratchet wheel and move the wedge-shaped blocks toward eachother, thereby lengthening the brake ring or band sufilciently to takeup any increase clearance due to the wear ofthe brake lining since thelast automatic adjustment.

If in the interval-between successive reverse braking adjustments-theclearance between the brake drum and brake ring becomes so excessive asto loose the desired pedal serve, an emergency adjustment suflicient totake care of a temporary thermal expansion may be eilected during theoperation of forward braking, by setting the member'288 in such positionthat any substantial excess movement of the link 282 will bring thismember into engagement with the lug 288 after the collar 288 has passedunder the head of the lug, and thereby move the pawl lever to aproportional degree. The amount of temporary adjustment thus effectedcan be limited to any ex-' tent desired, so as to avoid danger ofdragging of the friction surfaces.

Another embodiment of the invention is illustrated in Figures 6, '1 and10. In this embodiment a backing plate 888 has associated therewith arotatable drum 882. The backing plate has thereon an anchor 888, and afriction elepivoted thereto an operating lever 8 connected 'as bya rod8" to the separable end of the secondary shoe 888, and the forceapplying end of the operating lever 8l8 has attached thereto a dragcable 828 extending through the backing plate to a suitablepoweroperating means.

The structure shown isadaptable to a front .wheel brake in which aconsiderable part of the drum chamber is occupied by the king pinmounting. The take up adjustment for the two shoes 888 and 888 comprisestwo oppositely disposed wedges 822 and 828 interposed between thearticulated ends of .the shoes and concurrently movable toward eachother bya right and 'left hand screw 828' on a hollow tubular member828. This member revolves freely on an elongated stud shaft 888pivotally supported on a bracket 882 secured to the backing-plate, andthe tubular member has thereon a ratchet'wheel 888.

A drum 888 is positioned for rotation on the shaft 888. The drum carriesa pawl 888 adapted to engage with the teeth of the ratchet wheel.

- A fine'wire cable 888 is connected at one end to a tension spring 882attached to the backing plate. This wire passes once around the drum'volved thereby spreading the bracket andaround a pair of guide pulleys888 and 888 to a slotted fork 888 embracing a pin 888 in the forceapplying end of the operating lever 8l8.

The guidepulley 888 is mounted on the long arm of a bell crank lever 882pivotally supported ona slotted bracket 888 which may be clamped in thedesired position on the backing plate by a cap screw 888; and the shortend of the lever is loosely engaged by two pins 888'and 888 carried bythe webof the primary shoe 888. The effective length of the cable 888between the bracket 882 and the fork 888 may be adjusted by a slidingcollar 882 which may be secured at any desired point on the cableby aset-screw 888. The cable ,8 passes through a coil spring 888 interposedbetween the bell crank lever 882 and the fork 888. .The drag cable 828,passes through a coil spring 888 interposed between a clevis 888connecting the drag cable to the operating lever and an abutment 818 onthe backing plate.

Mode of operation. when the vehicle is moving forwardly the brakedrum isrevolving in the direction of the arrow A, and when the brake is appliedby pulling the dragcable 828, the toe end of the primary shoe is movedaway from the anchor pin 888 by counterclockwise rotation oftheoperating lever 8" about its fulcrum, and the heel of the secondary shoeis held in engagement with anchor. both by the pull of a spring 812connecting the primary shoe to the backing plate and which is strongerthan a companion spring 812 connecting the secondary shoe to the backingplate, and also by the wiping action of the revolving drum.

The counterclockwise movement of the primary shoe rotates the lever 882in the same di-.

rection, and thus shortens the distance between the guide pulleys. Thispermits the slotted fork 888 to move upwardly,'under the'thrust of thecompression spring 888 between the-bell crank lever 882 and the fork,and carries the outer terminus of the slot beyond to the normal .rangeof movement of the associated-pin'in the force applying end of theoperating lever.

Under these conditions there will be no pull exerted on the cable 888,and therefore, no movement of the pawl drum 888; In the operation ofreverse braking the primary shoe will be held in anchored engagement bythe reverse rotation of the brake drum and the bell crank lever 882 willtherefore be locked in the full line position. Under such conditions therotation of the operating lever which rocks on its fulcrum will bringthe pin in the end of that lever into engagement 1 with the upper end ofthe slotted member 888 and will rotate the pawl drum by an amount thatcan be controlled andregulated by the fadjustment of the collar 882.

When the brake is released, the drum 888 will be returned to itsoriginal position by the pull of the spring 882 and in this returnmovement the ratchet wheel and the screw 828 will be reshoes by theamount requisite to compensate for a predetermined degree of wear of thebrake lining.

If it is desired to provide for an emergency adjustment that willprevent a loss of pedal re-' serve-when the brake drum has beensubjected to an excessive heating on forward braking-the bracket 888 ismoved radially inward so as to increase the length of the short arm ofthe bell crank lever and correspondingly reduce the movement of theguide pulleys. This will hold screwr4l6 and the anchor.

vention is applied toa single anchor full wrapping band brake. In thisembodiment a fixed support 400 has associated therewith a rotatable drum402. The support has positioned thereon an anchor 404 and a frictionelement'adaptable for cooperation with the drum including a splitband4ll6 secured to thelbacking plate as by suitable return springs 408and H0, and provided on its separable ends with reinforced shoulders H2and H4 adaptable for engagement with the anchor. As shown, a hollowscrew M6 is threaded into the reinforced shoulder 4l2 on'the secondaryend of the band. The screw 6 en a es an L shaped member 8 interposedbetween the The screw 6 is provided with a toothed head 420 and themember H8 is slotted at one side to receive a reciprocable bar 422. Thisbar carries a reverse pawl 424 adapted to engage the teeth on the head420.

An operating lever 426 has one end positioned between the shoulder M4 onthe primary end of the band and the anchor 404. The other end of theoperating lever has attached thereto a clevis 428 to which issecured adrag cable 43!! passing through an abutment 432 on the backing plateto-a power operating means, not shown.

The cable has thereon a coil spring 434 interposed between the clevisand abutment.

The operating lever is connected by a bar 436 to the member 8 and thelever is provided with a bracket 438 which carries an adjusting screw440 adapted to engage an i. shaped lever 442 having one leg pivoted onthe backing plate and its other leg provided with an adjusting member Inoperation the brakes are applied by pulling on the cable 430 and therebyrocking the operating lever 426 in a counterclockwise direction. Thecable pull tends to rotate the entire brake ring or band in acounterclockwise direction about the axes of the brake drum, and if thedrum is moving in the direction of the arrow A (which corresponds toar'forward movement of the car) the toe end of the band will be movedaway from the anchor while the heel end together with the member 4|! isheld in pressure engagement therewith. The accompanying movement of theoperating lever will cause the end of the screw 440 to engage the lever442 and rock it in a counterclockwise direction; but this action willnot normally affect the adjustment elements because the path of movementof the adjusting member 444 is to one side of the pawl bar 422. However,when the car is moving backwardly and the brakes are applied the primaryend of the band is held against the anchor by the reverse rotation ofthe drum and the heel or secondary end of the band together withthemember 8 are carried as a unitaway from the anchor; and the inner end ofthe pawlbar 422 is thus brought into-line with the adjusting member 444.

The rocking of the lever .442 by movement of the automatically effectingnormal adjustment of the operating lever, now effects an outward move-'-ment of the pawl bar 422 which is controllable in amount by theadjustment of either or both of the members 440 and 444.

When the brakes are released, the pawl bar 422 5 is returned to itsneutral position by a suitable compression spring and the adjustingscrew 416 is rotated sufliciently to compensate for a predeterminedamount of brake lining wear.

If desired a limited and controllable amount 10 of emergency adjustmentcan also be eifected in forward braking by so setting the screw 440 thatany excess or abnormal movement of the operating lever 426 will bringthe intermediate part of the lever 442 into engagement with the lowerend of the pawl bar 422, and produce a slight outward movement thereof;but this emergency adjustmerit should never be sufficient in amount toresult in a dragging of the friction surfaces when the brake drumassumes its normal diameter. Or stated inanother way the emergencyadjustment should expand the brake ring by something less than thenormal clearance between the friction surfaces when'the brakes are inthe off position.

Although this invention has been described in 25 connection with certainspecific embodiments, the principles involved are susceptible ofnumerous other applications that will readfly occur to persons skilledin the art. The invention is, therefore, to be limited only as indicatedby the scope of the appended claims.

Having thus described the various features of the invention, what weclaim as new and desire to secure by Letters Patent is:

1. A brake comprising friction elements, an adjusting device connectingthe friction elements including a pinion, a slidable member having alongitudinal slot receiving the pinion, a springpressed pawl carried bythe member engaging the pinion, a. lever pivotally connected to themember, means for actuating the friction elements including a tensionmember moved difierently in forward and in reverse braking, and meansactuated by the tension member for trans mitting force to said leveronly on reverse brak 2. A brake comprising friction elements, anadjusting device connecting the friction elements including a pinion, aslidable member having a longitudinal slot receiving the pinion, aspring- 50 pressed pawl in the slot engaging the pinion, a

,lever pivoted to the slidable member, a stop for limiting the movementof the lever, an operating cam for the friction elements, a cableconnected to the cam and moved diiferently in forwardand in reversebraking and a device operably connectby operative engagement with saidpart when so moved in reverse braking and means for effecting'emergencyadjustment of the elements on forward braking.

4. A brake comprising friction elements having applying means includinga part moved differently in forward and in reverse braking, means forelements by operative engagement with said part when so moved in reversebraking, and means for effecting emergency adjustment of the elements onforward braking. v

5. A brake comprising friction elements having '7 in reverse braking,and emergency means for adjusting the friction elements operable only onforward braking.

1 6. A brake comprising-friction elements having associated therewith apart moved further in reverse braking than in forward braking, means forautomatically effecting normal adjustment of the friction elementsoperatable only by engagement with said part in reverse braking, andemergency means for adjusting the elements operatable only by engagementwith said part when moved excessively in forward braking.

7. A brake comprising automatic means for adjusting the frictionelements of the brake including separable parts relatively movable inintersecting paths when braking in the reverse direction and in pathswhich do not normally intersect when braking in the forward directionand which operate said means when they engage each other. i

8. A brake comprisingfriction elements, actuating means movablewith thefriction elements during reversebraking only," an adjusting deviceincluding a pinion connecting the friction elements, a slidable memberhaving a longitudinal slot receiving the pinion, means normallyseparated from the actuating means and engaged thereby during reversebraking only. to move the slidable member, and a spring-pressed pawl inthe slot engaging the pinion.

9. A brake comprising friction elements, an adjusting device including apinion connecting the friction elements, a slidable member having alongitudinal slot receiving the pinion, a spring-- pressed pawl in theslot engaging the pinion, a part moved differently in forward and inreverse braking, and a lever operably connected to the slidable memberand positioned to be actuated by said part when moved in reversebraking.

10. In a vehicle brake having friction elements,

automatic means for adjusting the friction ele-- ments includingnormally separated parts relatively movable in intersecting paths whenbraking in the reverse direction and in paths which do not normallyintersect when brakin in the forward direction and which operate saidmeans when they engage each other, and means to per- 7 'mit said-partsto'engage-when brakinginthe forward direction when apredeterminedadiustment is required. a

11. In a vehicle brake comprising friction elements, an adjusting deviceconnecting the friction elements including a wedge positioned betweenadjacent ends of the friction elements, a

"pinion having teeth said pinion being onerabi connected to the wedge, aslidable member hav-- ing a longitudinal slot receiving the pinion, aspring-pressed pawl inthe slot the pinion, a part moved differently inforward and in reverse braking, a lever operably connected to theslidable member and separated from but posiber, friction means adaptedto engage the stationarii member, operating mechanism movable with thefriction means when in the reverse direction only, automatic adjustingmeans for the friction means positionedin the line of movement of theoperating mechanism when moved with the friction means in reversebraking.

13. In a brake mechanism, a stationary member, friction means adapted toengage the stationary member, operating mechanism movable V with thefriction means when braking in the reverse direction only, automaticadjusting means including a pinion having right and left-hand threads.engaging spaced wedges for increasing in theline of movement of theoperating mechanism when moved with the friction means in the pinion,yielding means urging the movablemember toward oneextreme position,means including a linkage to shift the movable member,

means to apply the brakes including an actuating member operabledifferently in forward and reverse braking, and a. stop memberpositioned to be engaged by said linkage.

15. In'a brake mechanism, friction means, ad-

justing means including, a pinion havlng right and left-hand threads forvarying the,eflective length of the friction means, a movable memberhaving a pawl yieldin'gly urged into contact with the pinion, yieldingmeans urging the movable member toward one extreme position, meansineluding a linkage to shift the movable member, said yielding meansbeing connected to the linkage, means to apply the brakes including anactuating member operable differently in forward and reverse braking,andan adjustable stop memthe II;- ,iu

ranged at times'to engage saidlinkage.

16., In. a vehicle broke, a stationary backing plate, a rotatable brakedrum, friction means adaptedtoengagethedrmadjustingmeans including apinion havim right and left-hand threadsforchaningtheeifectivelengthofthe the length of the friction means andpositioned inotionmeanaammwneeimeaiomepmf ion, a movable member havingapawl adapted to engage the ratchet wheel, means-including alinkurgingthemovablemembertooneextremeposition, means includingacam'moved diil'erently -ageto shiftthe movable member, yielding meam.

inforward andreversebrakingfcrm'ging-the'frictionmeansintocontactwiththedrum,anad-JustabIemembetflxedtothecamandadaptedto. engage the linkage when movedinone manner of movement of the com to urge the friction means intocontact with the drum and to avoidensaglngsaidlinkagewhenmovedintheother manner-of movement of said cam.

17. A brake mechanism having a stationary backing plate, a rotatablebrake drum, friction pinion, amovable member having a pawl adapted toengagethe ratchet wheel, means including. a

linkage-to shift the movable member, yielding means carried by thelinkage urging the movable member to one extreme position, meansineluding-a cam moved differently in forward and .reverse braking forurging the friction means into contact with the drum, an adjustablemember 2,086,077 fixed to the cam and adapted to engage said link agewhen moved to urge the friction means into contact with the drum inreverse braking and to avoid engaging said linkage when movedto applythe brakes in forward braking.

18. A brake comprising friction elements which are shiftable to anchorat one end in forward braking and the other end in reverse braking, andautomatic adjusting means for said friction elements said means havingparts controlled by the shifting of the shoes whereby 'said'meansadjusts the friction elements to normal clearance only when they areapplied in reverse braking and to greater than normal clearance whenapplied in forward braking. e

19. A brake comprising friction elements which are shiftable to anchQrat one end in forward braking and the other end in reverse braking, ap-

plying means for said friction elements, an adjustme'nt for saidfriction elements operated-by excessive movement of said applying means,means controlled by the shifting of said friction elementsinterconnected with said adjustment so that the excessive movement ofsaidapplying means necessary to operate'said adjustment is .materiallygreater in forward braking than in reversebraking. l

20. A brake comprising friction elements which have one movement whenapplied .in forward braking and a different movement in reverse braking,applying means for said friction elements, an adjustment for saidfriction elements, actuating means for said adjustment operated byexcessive movement of said applyingmeans,

and means controlled by the movements of the friction'elements andinterconnected with said actuating means to shift it so that theexcessive movement of said applying means necessary to operate saidadjustment is materially greater I I in forward braking than in reversebraking.

2 1; A brake comprising friction elements which have one movement whenapplied 'in forward braking and 'a different movement in reversebraking, applying means for the friction elements, an automaticadjustment for the friction elements having an actuating memberpositioned for forward and reverse braking in accordance with themovement of said elements, and means operated by the applying meansadapted to operatively engage said member and actuate the adjustment andarranged so that greater applying movement is necessary to engage saidmember when it is positioned for forward braking than when it ispositioned for reverse braking." v 22. A brake comprising an anchor, afriction element anchoring thereon in forward braking and moving awayfrom the anchor in reverse braking, and means controlled by movementofment, and means controlled by the reverse-brakingmovement of said partof the element for actuating the adjusting means only on reverse brakingand which includes parts operable in an emergency for actuating theadjusting means only on forward braking.

ROY S. SANFORD. FRANK L. O. WADSWORTH.

